^^ no it doesnt matter and all the machines have the target heart rate on them.I personnally suggest swimming. 2 laps at max effort=20 min on the tredmill at 4.5. Honestly i think the eliptical is for people with bad knees or backs if you can hit the tredmill hard or swim do it!
Edit: I have a great diet. Iv lost about 16 pounds in a week and a half. Ill type it up if your interested..